Zedd and Rahjah- my 5.5 month old has been doing the EXACT same thing for a month now and driving me bananas. I have found the best thing to do it ignore what I did before (timing, naps etc), and now I put her down for a nap as soon as she yawns/rubs her eyes. She usually protests so I turn the vacuum on or the radio on static outside her room. She stops grizzling to listen then falls asleep for 45 mins to 1 hours. I do this up to 4 times a day and it has hugely improved her night sleep to no end. I don't let her cry it out either. But I swear by day naps. If not, she gets overtired and come 9pm (after having gone to sleep at 7pm) she is awake and screaming. Do whatever you can for now to get them to sleep during the day.